1. Field of the Invention
Embodiments of the present disclosure relate to the field of device manufacturing. More particularly, the present disclosure relates to an improved method and apparatus for removing vertically oriented substrates from cassettes.
2. Discussion of Related Art
Attempts have been made to automate the handling and transfer of thin substrates during ion implantation, sputter coating and other processes both for preventing contamination, abrasion or damage to the substrates and for achieving a high throughput in terms of the number of substrates processed per unit time. Often, substrate cassettes are provided to hold a plurality of discs in vertically facing alignment.
The cassette can be a generally rectangular frame having a pair of parallel side walls which stand facing each other and are grooved so that standard-sized disk-shaped substrates can be held edgewise. The grooves on the side walls of the cassette are vertical and parallel to each other so that the substrate can be moved into and out of the cassette while maintaining its upright vertical position.
An automated substrate transfer system may be used to remove substrates from the cassette. For example, a movable picker can pass through the cassette to engage a substrate and remove it from the cassette. The substrate can then be transferred to processing chamber where one or more deposition, implantation or other treatment processes can be performed. The substrate may remain engaged with the picker throughout the transfer and processing steps, or it may be transferred to a separate carrier for either or both of the transfer and processing steps. Once processing is complete (or a desired processing step is complete), the picker may return the substrate to the cassette or other carrier, where the processed substrates remain while the movable picker removes a next substrate to be processed. This continues until all the substrates have been processed.
A problem with current substrate transfer arrangements is that the picker typically either engages the outer diameter of the substrate or it contacts the substrate face. If the picker fails to perfectly engage the outer diameter, the substrate can slip off the picker, causing damage. For instances in which the picker is configured to contact the substrate faces (similar to tweezers), the chances that face damage will occur is undesirably increased.
Thus, there is a need for an improved system and method for removing substrates from a cassette. The system and method should provide consistent and reliable engagement of a substrate to minimize the chance for damage to occur to the substrate, either through dropping, through contact with of the substrate face, or through engagement with other substrates.